1. Field of the Invention.
The present invention relates to pallet-making machines, and in particular to nail-driving chucks for use in a pallet-making machine.
2. Description of the Prior Art.
Wooden pallets, as they are known today, first came into widespread use during World War II as a result of the need of the United States Navy to move large amounts of goods in short periods of time with forklift trucks. The usage of wooden pallets has increased every year since that time.
In 1987, it is projected that about 380 million new wooden pallets will be built in the United States. Pallets consume about twenty percent of the lumber that is used in the United States annually. The manufacture of pallets is second only to the construction industry and is ahead of all other industries in the use of lumber. Wooden pallets consume about fifty percent of the hardwood lumber used annually in the United States.
To satisfy the high demand for wooden pallets, machines have been developed which manufacture pallets on a semi-automatic or automatic basis. An example of automated pallet-making equipment is shown in the Colson U.S. Pat. No. 3,945,549.
The Colson patent shows a type of pallet-making machine which uses a vibrating bowl to feed bulk nails to a picker mechanism, which individually feeds the nails to a chuck. Each time a nailing operation is to take place, a ram drives the nail being held by the chuck into the boards located below the chuck.
It is extremely important that the nails which are driven into the boards of a pallet be countersunk, i.e. the head of the nail must be driven into the wood so that it does not protrude above the top surface of the board. Countersinking is of critical importance because many pallets are used for the movement of bagged goods or other packaged material. If nail heads are protruding from the pallet, there is a danger that the heads will puncture the bags, which results in spilling of the contents of the bags.
Several factors complicate the ability to countersink nails on a consistent basis. First, the thicknesses of the boards being nailed can vary. Saws do not always cut the boards to a uniform thickness. Second, the condition of the wood can vary substantially. During the summer, when the boards are warm, it is much easier to drive nails into the wood than it is in the winter, when the boards may be very cold or even frozen.